Abstract: For directory services for telecommunication, a data network, a terminal connected to the data network, at least one database in the data network, and a device for interactive communication between the terminal and the network regarding the database are provided. The database includes catalogue data regarding subject information about persons/families/companies, so that catalogue searches using different search criteria can be done. The desired information and adequate search criteria may be asked for from the terminal. The search is performed, and the desired catalogue data is presented visually on a display of the terminal asking for the subject information. The device also includes a reliable database outside the network, accessible and changeable only by admitted operating staff devices, and a transmitter for transmitting information from the reliable database to at least a reliable part of the database inside the network.